In the harvesting of crops it is desired that the grain be separated from other elements or portions of the crop, such as from pod or cob fragments, straw, stalks, and the like. Agricultural combines typically have employed a rotary threshing or separating system for separating and segregating the grain from such other crop elements or portions. In general, rotary threshing or separating systems are so designed that, as threshing occurs, the resulting crop material is typically caused to fall or be conveyed to a clean grain and tailings conveying system, sometimes also referred to as a collecting and conveying system, or even more simply as a conveying system, for further processing, which processing typically includes the feeding of such resulting crop material from the rotary threshing or separating system onto an underlying vibratory cleaning system or onto one or more conveyors for conveyance to such a cleaning system.
The cleaning system typically includes a set of stacked sieves or shoes that are reciprocally moved, usually in the fore and aft directions, to separate or sift the grain from tailings and material other than grain (MOG). With many combines, as the grain is cleaned from the MOG, it falls through the sieves and drops onto or into one or more underlying clean grain pans that are disposed below the sieves, which pans feed the clean grain to an intersecting, cross, generally laterally extending, clean grain conveyance trough, sometimes referred to as the clean grain auger trough or, more simply, the clean grain trough.
The laterally extending clean grain conveyance trough receives the clean grain conveyed thereto from the clean grain collecting troughs and typically has associated therewith a conveyance mechanism, often in the form of an auger extending therethrough, for moving and delivering the clean grain in such clean grain conveyance trough to an elevator that carries the clean grain up to a clean grain tank.
During the vibration of the sieves, air is blown upwardly and rearwardly through the sieves to carry lighter elements of the MOG, or chaff, away. The heavier elements and tailings that are too large to fall through the sieves and too heavy to be blown away are caused to be moved by the vibrations, generally rearwardly along the top surfaces of the sieves, towards and over rear edges of the sieves to fall onto a tailings pan located below and extending somewhat beyond such rear edges. The tailings pan, similarly to the clean grain pan, feeds the tailings to an intersecting, cross, generally laterally extending, tailings conveyance trough, sometimes referred to as the tailings auger trough or, more simply, the tailings trough.
The sidewardly extending tailings conveyance trough receives the tailings conveyed thereto from the tailings collecting pan and/or troughs and has a conveyance mechanism, often in the form of an auger extending therethrough, for moving and delivering the tailings to a tailings return conveyor operable for carrying the tailings upwardly, back to the cleaning or separating system of the combine, for reprocessing, including further threshing of the tailings.
For a number of years now, transverse or cross-flow fans of various designs have been advantageously employed with agricultural combines to provide the air that is blown upwardly and rearwardly through the sieves to carry the chaff away from the grain and tailings deposited onto the cleaning system sieves. Such chaff is typically blown into an optional chaff spreader, operable for distributing the chaff over a desired swath of the field from which the crop is cut, or directed into an optional chopper, operable for mixing the chaff with straw for chopping and distributing such mix, or simply directed downwardly onto the field through a rear opening of the combine.
Transverse or cross-flow fan assemblies are well known in the art, and such fan assemblies typically have included axially spaced disk-like members that support a plurality of elongated fan blades in some form of cylindrical pattern or array, often with as many as thirty-six fan blades disposed in a cylindrical arrangement about the axis of rotation of the fan. With some fan assemblies, straight and cross-sectionally curved fan blades have been disposed with the tips of the blades extending generally parallel to the axis of rotation, which fan blade configurations are generally hereinafter referred to as axially aligned fan blade arrangements. In more recent years, in efforts to reduce fan noise, newer types of transverse fan assemblies have been developed in which the fan blades in a number of fan assemblies have, instead, been angled. One example of a transverse fan assembly that has been advantageously employed in combines and which utilizes an angled blade arrangement, with the fan blades disposed in a chevron blade arrangement, is found in U.S. Pat. No. 5,599,162.
Transverse fans have proven particularly useful in combine cleaning systems because such fans can produce a wide stream of air that can be directed upwardly toward the cleaning sieves of the combine cleaning systems but require relatively little space. Such fans, in typical agricultural combines, are disposed such that their air outputs are below the sieves of the cleaning system, and, so, are positioned close to the ground over which the combine moves.
As will be appreciated, rocks and other debris commonly found in fields can be detrimental to the normal high speed rotational operation of fan blades, and broken and/or bent fan blades can affect fan performance, and consequently, the overall efficiency of a combine in which a transverse fan assembly is installed. Accordingly, when transverse fan assemblies are employed with typical combines, the fan blades are normally protected by installing the fan within a fan wrapper or air plenum, with the fan being rotatably mounted within an inner chamber of the air plenum to operably drive air between an air inlet and an air outlet.
Desirably, such transverse fans, as employed in combines, will provide a relatively wide output of air, of preferably uniform or consistent flow along the expanse of the fan. Unfortunately, inconsistencies in the flow of output air can arise for various reasons, including due to “end effect” air characteristics and the existence or occurrence of obstructions in the air pathway through the air inlet to the air inlet entryway.
In general, especially for straight-bladed transverse fan assemblies whose fan blades are disposed in axially aligned fan blade arrangements, as the fan rotates forwardly air is drawn in an air flow pathway through the air inlet towards the air inlet entryway at the leading edge of the air plenum where such leading edge is disposed closely adjacent to the outer periphery of the rotating fan, and thereafter through the fan to the air outlet, all in approximately the same line. Thus, if a volume of air enters 10 inches from the end of the fan, it will be expected to exit approximately 10 inches from the end of the fan.
For fan assemblies that, instead, have a chevron blade pattern, air is drawn in an air flow pathway into the fan in much the same fashion, but, to improve fan performance by lessening end air effects while still providing a generally uniform air distribution across the expanse of the fan, the resultant flow of air off of the fan blades as the fan rotates forwardly is directed somewhat outwardly toward the fan ends, thereby perhaps occasioning some slight shift in the air flow path from the air inlet to the air outlet. In some instances, improvement in the air flow volume realized at the ends of the fan may thus result in some degradation in the air flow volume near the center of the fan.
Additionally, the existence or occurrence of an obstruction in some area of air pathway to the air inlet entryway will affect the air flow volume being provided to the fan downstream from such obstruction, resulting in an air flow void or deficiency or discrepancy at locations along the expanse of the fan as inlet air is being provided thereto, thus impacting the corresponding air flow volume at the air outlet and resulting in undesirable non-uniformity in air flow volume along the expanse of the fan and a lessened efficiency in the operation of the cleaning section and in the separation of the chaff from the other crop materials. For purposes of further discussion herein, reference to an air flow void should be considered to encompass not only a lack or absence of air flow at a particular location but also any lessened or deficient air flow at that particular location, and should be broadly construed.
Desirably, then, it has been recognized that it would be beneficial if additional air flow could be introduced into the air inlet, or the air pathway to the air inlet entryway, especially into an area of deficient air flow volume, to effect such an air flow distribution into the fan across the expanse of the fan that a more uniform air flow can be realized at the air outlet. Unfortunately, it has been found that simply introducing air into the air pathway from the opposite ends of the fan does not result in the desired uniformity of air flow because the air flow from the opposite ends across the fan undesirably disrupts the fan output.
Consequently, there has remained a desire for a transverse fan assembly that permits and provides for the supply and introduction of supplementary air into the air inlet for the fan in such a way that infill of air flow voids or deficiencies in the air flow pathway can be effected so as to effect a desired, generally more uniform, output air flow pattern across the entire expanse of the fan instead of undesirably disrupting the fan output. Combine operators have continued to seek such a fan construction and a method of use thereof that can provide the more uniform flow of air desired, including in the event of obstructions in the air pathway to the air inlet entryway to the fan, which construction preferably will also include features for selectably altering to some extent the air flow volume introduced into the fan at one or more locations along the expanse of the fan.